Web services (WS) are designed to support interoperability across middleware platforms from different vendors. As a result, the XML-centric, message- and standard-based, WS technology is one of the most popular bases for the realization of the Service Oriented Architecture (SOA). A new approach to architecting IT systems, SOA is based on loose coupling and dynamic binding between services representing applications of one or more enterprises. Services are defined at an abstract level such that service consumers can bind to these definitions. Service providers implement these definitions and publish the details necessary for the consumers to connect to the services. Finally, service consumers must have a way to reliably find the services they need. The WS technology currently offers a solution to the bind/publish/find needs of the SOA architecture and they are evolving towards addressing these needs even better, with improved security and quality of service features or with enhanced service discovery and composition facilities based on semantic technologies.
Major trends in business IT, such as outsourcing and continuous business process optimization, are among the reasons why the importance of the SOA approach is expected to increase in the foreseeable future. To satisfy the requirements of an increasingly mobile workforce, many SOA implementations include devices with limited computing or communication capabilities, such as smart phones, PDAs or UMPCs.
In the pervasive domain, WS technology is becoming one of the favorite solution for exporting the capabilities of mobile devices or of the environment, and for service discovery and invocation. Semantic extensions to WS technology allow the dynamic generation of personalized UIs, which enable independent deployment of environmental services and mobile devices.
The success of WS technology is to a large extent due to its reliance of XML and its self-describing characteristic. Web Service descriptions, which define service operations and their messages, the data types used in these messages, and the service endpoints are defined using XML. Service policies, repositories and more recent semantics are also described using XML-derived languages. When using SOAP, which is the typical WS messaging framework, a large part of the message is in XML. In contrast to WS-related definitions, where the verbose nature of XML does not introduce a performance bottleneck, the performance of SOAP messaging is negatively impacted by XML-related processing and communication overheads. Thus, it is desirable to have a mechanism for optimizing SOAP.